Use mirror-free LRU test for dart2js

tests/lib/mirrors/lru_expect.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import "dart:mirrors";
 import "package:expect/expect.dart";
 
-newLRUMapWithShift(int shift) {
-  var lib = currentMirrorSystem().libraries[Uri.parse("dart:_internal")];
-  var cls = lib.declarations[#LRUMap];
-  return cls.newInstance(#withShift, [shift]).reflectee;
-}
-
-main() {
-  Expect.throws(() => newLRUMapWithShift(0), (e) => e is Exception);
+expect(lruMapFactory) {
+  Expect.throws(() => lruMapFactory(0), (e) => e is Exception);
 
   for (int shift = 1; shift < 5; shift++) {
-    var map = newLRUMapWithShift(shift);
+    var map = lruMapFactory(shift);
     var capacity = (1 << shift) * 3 ~/ 4;
     for (int value = 0; value < 100; value++) {
       var key = "$value";
       map[key] = value;
       Expect.equals(value, map[key]);
     }
     for (int value = 0; value < 100 - capacity - 1; value++) {
       var key = "$value";
       Expect.equals(null, map[key]);
     }
     for (int value = 100 - capacity; value < 100; value++) {
       var key = "$value";
       Expect.equals(value, map[key]);
     }
   }
-}
+}